1. Field of Use
The present invention relates to power units used to drive manually operated conventional wheelchairs, and more particularly, to novel power units that are automatically operated from a control switch to be attachable to and detachable from conventional wheelchairs for producing power driven wheelchairs.
Attachable power systems for manually operated wheelchairs are well known in the art. Various configurations have been designed with a variety of attachment methods, control methods, and detachment methods that allow the wheelchair to be converted back to a conventional manually operated wheelchair.
In all instances of prior art design known to the inventor the conventional wheelchair must be fitted with brackets, clamps, bars or sockets, or the apparatus must be pre-sized and manually configured to be custom fitted to a particular variant of a conventional manually operated wheelchair. In particular instances, the rear wheels must be removed to add specialized hubs, or powered hubs are added with the rear wheels still attached. In many instances of the prior art, both wheelchair modifications and pre-sizing of the power apparatus are required to adapt the power apparatus to the wheelchair. Adding attachment accessories to the wheelchair or having to pre-size the assembly requires tools, time and intervention on the part of the user or others that severely limits the convenience of use of the apparatus.
In the instances of a powered apparatus mounted under the wheelchair, the frame of the wheelchair has been the preferred location of attachment. Using the frame for attachment can place lateral or torsional stress on the frame of the wheelchair limiting the service life of the wheelchair. In many cases, holes must be drilled into the frame of the wheelchair to accommodate the attachment means, further limiting the service life of the wheelchair. Wheelchair users are very protective of their wheelchairs and are reluctant to make alterations or add attachments that may damage or reduce the service life of their wheelchair.
Although often referred to as xe2x80x9cstandardxe2x80x9d, conventional wheelchairs of the manually operated type are manufactured by more than 60 different companies worldwide and embody significant variations in height, width, and frame layout. These variations have heretofore represented a difficult challenge to the manufacture of a universal or near-universal power apparatus that can be quickly and securely attached and detached from a wide variety of conventional manually operated wheelchairs.
If a wheelchair power apparatus is only going to be used by an individual user on a single specific wheelchair then the inconvenience represented by prior art designs is limited in frequency. However if the power apparatus is to be used by different wheelchair users with different wheelchairs on a regular basis, such as in a retail sales environment, then the inconvenience imposed by prior art designs becomes intolerable. Retrofitting of the wheelchair or pre-sizing of the device places a difficult burden on the user.
2. Background Setting of the Prior Art
Various types of electrical motor or engine powered drive units for wheelchairs are known or proposed in the prior art. U.S. Pat. No. 3,921,032 describes a front mounted drive apparatus that attaches to tubes that have been added to a conventional wheelchair in proximity to the armrests of the wheelchair. A ramp is used to raise the front wheels of the wheelchair, thus raising the receiving tubes to match the attachment bars of the apparatus. The apparatus is manually aligned by the user or attendant to receive the attachment bars.
U.S. Pat. No. 3,921,744 proposes a device that uses added receiving sockets mounted on the outer front frame of the wheelchair.
U.S. Pat. No. 4,386,672 proposes an apparatus that mounts to the under frame and crossbars of a foldable wheelchair. The apparatus width is preset. The user or attendant manually aligns and attaches a connector beneath the seat of the wheelchair. Throughout the prior art, one sees devices that require excessive intervention either by the user or a second party to prepare the propulsion device or the wheelchair for addition of a drive mechanism.
In a video by Stand Aid of Iowa Inc. describing a device called xe2x80x9cRoll-Aidxe2x80x9d, special brackets and lift bar are used to retrofit the wheelchair. Once retrofitted, the wheelchair is ready to accept the attachment of the Roll-Aid powering device. The wheelchair is rolled forward over the Roll-Aid and the brakes of the wheelchair are locked. The Roll-Aid is then put into reverse and attaches to the lift bar that was retrofitted to the wheelchair. A release cord is picked up off the ground and tied to the backrest or arm of the wheelchair.
Once the apparatus is attached, the brakes are released from the wheelchair and the Roll-Aid is ready to be put to use. When detachment is desired, the user locks the brakes on the wheelchair, reaches around the back or side of the wheel chair and manually manipulates the release cord. The video illustrates that the release cord is tied to the arm of the wheelchair as an attachment.
The lift bar required in the Roll-Aid retrofitting may prevent a foldable wheelchair from being folded until the bar is removed.
In the paper entitled xe2x80x9cManual Wheelchair Propulsionxe2x80x9d obtained from the web site cosmos.buffalo.edu/t2rerc, the author points out xe2x80x9cExperts and industry contacts mentioned power assisted add on units for manual wheelchairs as an area for further technology development and improvement.xe2x80x9d A selection of specifically noted problems with current art include:
Adding a power assist unit to a manual wheelchair will increase the weight of the wheelchair and may offset the distribution of mass or balance and center of gravity, possibly making it more difficult for the user to propel when the power assist is disengaged.
Heavy power assist units can stress the wheelchair frame if the wheelchair is not specifically designed to accommodate the unit.
Some of the units are cumbersome to attach and detach, requiring the assistance of a second person.
A selection of specific issues to consider in the area of improved power assisted propulsion technology noted in the report include:
Can the products work across a wide range of wheelchairs?
Can the unit be easily engaged and disengaged as a function of power demand?
Can the products be less cumbersome to attach and detach?
As will be seen in the sections that follow, the apparatus of the present invention addresses these areas of needed technological improvement noted by the University at Buffalo and addresses additional deficiencies noted in the prior art.
The primary object of the present invention is to provide a power apparatus for a conventional manually operated wheelchair that is easily attached to the wheelchair by the unassisted user without the use of tools and that is readily adaptable across the broad range of wheelchair widths, heights, and frame layouts currently on the market.
It is a further object of the present invention to provide an attachable power apparatus for a conventional manually operated wheelchair wherein the power apparatus self adjusts to attach to the front wheels of wheelchairs having various front wheel spacings, front wheel thicknesses, and front wheel diameters.
It is a further object of the present invention to provide an attachable power apparatus for a conventional manually operated wheelchair wherein the power apparatus has a very low center of gravity to provide for greater stability and safety. The apparatus of the present invention is attached to the wheelchair at the lowest possible point to improve the stability of a standard manually operated wheelchair when in use.
It is a further object of the present invention to provide an attachable power apparatus for a conventional manually operated wheelchair that allows the wheelchair to be turned in a radius defined by the length of the overall assembly of the wheelchair and the power apparatus when the apparatus is attached.
It is a further aim of the present invention to provide an attachable power apparatus for a conventional manually operated wheelchair that includes ramps to allow the front wheels of the wheelchair to ride up onto the apparatus, said ramps retracting from a deployed position to a non-deployed position until needed for dismount of the wheelchair from the apparatus.
It is a further object of the present invention to provide an attachable power apparatus for a conventional manually operated wheelchair that allows the user a degree of inexactitude in the wheelchair alignment with the apparatus before attachment.
It is a further object of the present invention to provide an attachable power apparatus for a conventional manually operated wheelchair that does not produce any lateral or torsional stress on the frame of the wheelchair when the apparatus is attached to the wheelchair.
The present invention provides a battery powered steerable tractor apparatus that includes a powered, self-adjusting attachment means allowing the apparatus to be interchangably attached to a broad range of conventional manually operated wheelchairs without the need for adding fittings to the wheelchair or manually pre-sizing the apparatus. As used herein, the term xe2x80x9ctractorxe2x80x9d is intended to include a pulling device as well as a pushing or supporting device that has the capability to move a wheelchair or other wheeled object.
A preferred form of the tractor apparatus of the present invention comprises a steerable wheel and controllable drive system, a pair of powered adjustable clamping means for attachment to the front wheels of a conventional wheelchair, a pair of self-contained ramps to position the front wheels of a manually operated wheelchair between the clamps of the attachment means, a powered linear actuator to activate the clamping means, one or more electric batteries or other suitable portable electrical power source, and trailing support wheel (or wheels) at the rear of the drive system.
The apparatus of the present invention attaches to a conventional manually operated wheelchair at the lowest possible point, the bottom of the front wheels. This method of attaching the tractor to the wheelchair produces an extremely low overall center of gravity in the resulting combined assembly. When the tractor apparatus is attached to a conventional wheelchair, the center of gravity of the unified wheelchair and apparatus is substantially lower than the center of gravity of a wheelchair alone. Accordingly, adding the tractor apparatus of the present invention to a wheelchair improves the stability of the wheelchair. This low center of gravity ensures stability in mount, use and dismount. Specifically, when in use, the tractor apparatus actually adds weight beneath the wheels of the wheelchair and lowers the overall center of gravity of the combined unit, improving stability.
The preferred embodiment of the present invention includes independent floating clamps that allow for a significant degree of inexactitude in placement of the front wheels of the wheelchair when mounting the wheelchair into engagement with the tractor drive device. Each of the clamps is free to move independently when activated to locate the object front wheel and apply clamping force to the wheel. This novel approach produces no lateral tensioning of the wheelchair frame or tires.
The apparatus of the present invention is applicable to manually operated wheelchairs of both the foldable and non-foldable types. The attachment mechanism of the present invention offers no interference with the foldability of a foldable wheelchair when not attached to the wheelchair.
The method of the present invention uses soft, conforming clamping means to engage the lower portion of the front tires, rim and spokes of the front wheels of a conventional manually operated wheelchair. The clamping surfaces are designed to provide a firm grip when in the clamped position without risking damage to tires, rims or spokes of the front wheels of the wheelchair.
The present invention provides free-floating wheel clamps that move independently of each other to accommodate front wheelchair wheels of various spacings and widths.
In the preferred embodiment, the tractor apparatus of the present invention provides a steering column with a handlebar, a speed control, a drive motor, a switch plate with a power switch and an electrical clamp control switch. The clamp control switch allows the user to activate the clamping means through the simple flip of the switch.
In an alternative embodiment, a joystick coupled with a powered steering mechanism can be substituted for the handlebars and speed control. The joystick embodiment employs a single steering and speed switch plus a switch to activate the clamping mechanism.
In yet another embodiment of the invention, the wheelchair is mounted upon a self-powered platform incorporating the novel front wheel clamping arrangements of the present invention.
The preferred form of the tractor apparatus of the present invention allows for threshold clearance of more than 1xe2x80x3 for home use. It can accommodate a large range of inclines. The apparatus controls provide self-braking when moving forward on a downgrade. The apparatus can be steered, stopped, and speed controlled in both the forward and reverse directions.
The tractor apparatus of the present invention offers the ease of use and control of a powered scooter while permitting the user to remain in the user""s personal, manually propelled wheelchair without the need to transfer to a scooter. Transferring to a scooter can be quite challenging and uncomfortable for the user and can lead to mishaps. With the apparatus of the present invention, the users maintain use of their own wheelchairs, which oftentimes are custom made and adapted to meet individual requirements.
The apparatus of the present invention is especially applicable in assisting wheelchair bound patrons to move about a retail environment. The user of a manual wheelchair can roll up onto a waiting tractor apparatus and attach to the apparatus with the simple flick of a switch. The user is then free to use the power unit to provide controlled motive power to the wheelchair while shopping. Since the user can achieve the clamping of the wheelchair without assistance and can further operate the powered wheelchair without assistance, anyone accompanying the user is free to pursue other activities.
When a user has finished with the apparatus, the user simply detaches and rolls off. A second user, even one with a differently sized wheelchair with a different distance between front wheels, can roll up onto and attach to the unit vacated by the first user. The second user switches on the clamping device and achieves secure clamping without having to manually modify the wheelchair or the tractor apparatus.
This ability to accommodate wheelchairs of various configurations overcomes many limitations imposed by prior art propulsion devices. The tractor apparatus of the present invention will additionally find ready use and fleet efficiencies in nursing homes, hospitals, sports venues, airports, and other public gathering places.
The platform version of the present invention permits a wheelchair to be fully supported above the rolling surface independently of the wheelchair wheels. The wheeled platform can provide greater mobility and a reduced turning radius as well as other maneuvering and control advantages.
The foregoing objects, features and advantages, as well as others, will be more fully understood and better appreciated by reference to the following drawings, specification and claims.